Electric field vector measurements via nanosecond electric-field-induced second-harmonic generation.

Electric-field-induced second-harmonic generation, or E-FISH, has received renewed interest as a nonintrusive tool for probing electric fields in gas discharges and plasmas using ultrashort laser pulses. An important contribution of this work lies in establishing that the E-FISH method works effectively in the nanosecond regime, yielding field sensitivities of about a kV/cm at atmospheric pressure from a 16 ns pulse. This is expected to broaden its applicability within the plasma community, given the wider access to conventional nanosecond laser sources. A Pockels-cell-based pulse-slicing scheme, which may be readily integrated with such nanosecond laser systems, is shown to be a complementary and cost-effective option for improving the time resolution of the electric field measurement. Using this scheme, a time resolution of ∼3  ns is achieved, without any detriment to the signal sensitivity. This could prove invaluable for nonequilibrium plasma applications, where time resolution of a few nanoseconds or less is often critical. Finally, we take advantage of the field vector sensitivity of the E-FISH signal to demonstrate simultaneous measurements of both the horizontal and vertical components of the electric field.